Process and device for the internal welding of plastic tubes

Abstract

The invention relates to a process for manufacturing plastic packaging in tubular form, which process comprises a wrapping step during which a laminate (11) is wrapped, an abutting step during which the edges (8, 9) of the laminate (11) are butted together and a fastening step during which said edges (8, 9) of the laminate (11) are welded together, characterized in that a bead (12) of plastic in the molten state is extruded and deposited on the internal face of the packaging so as to cover at least the weld zone (10) defined between the edges. The energy needed to produce the weld (10) comes from the plastic bead (12).The invention also relates to packaging obtained from the aforementioned process and to a device for implementing said process.

Description

FIELD OF THE INVENTION[0001]The invention relates to the field of tubular packaging, especially consisting of a wrapped plastic laminate. More precisely, the invention relates to wrapped laminates, the edges of which do not overlap.PRIOR ART[0002]The welding of the edges of a laminate so as to obtain a tubular body usually takes place with an overlap. See for example German Patent Application DE 2008085.[0003]When it is desired to place the edges face to face, a gap is left between them which is filled with a material, such as a strip of plastic, the strip acting as a welding element. See for this purpose European Patent Application EP 0 000 643.[0004]However, there is a need to bring the edges into direct contact with each other (butt welding), for technical and aesthetic reasons. Butt welding provides better continuity and homogeneity of the material constituting the wall of the packaging. In particular, it avoids contact between the product placed inside the tube with a barrier l...

AI Technical Summary

Benefits of technology

[0019]Advantageously, a device may be used for preheating the edges, for example by contact, having the effect of increasing the temperature of the two edges of the laminate, thus facilitating or improving the welding conditions.

[0020]Alternatively, or in addition, another device is used which is provided with a hot-air blower so as to maintain the ambient air around the bead at a temperature of several hundred ° C. and consequently to avoid a drop in temperature of the bead as it passes from the exit of the extrusion head to the point where the bead is shaped.

[0021]According to one variant of the invention, the edges of the laminate are cut obliquely, this having the effect of increasing the lateral contact area of the laminate in the weld zone. Such a configuration also enables the quality and the strength of the weld to be influenced.

[0022]In another variant of the invention, a bead is extruded with a shape other than a cylinder, for example in the shape of an upside down T, thereby facilitating the shaping of the bead during welding.

[0023]Another variant of the invention consists in using a bead of coextruded plastic (coextruded with a barrier material at the centre of the bead) so as to also guarantee, in the zone defined between the edges of the laminate, good barrier protection from the external environment of the tube.

Problems solved by technology

However, there is a need to bring the edges into direct contact with each other (butt welding), for technical and aesthetic reasons.

Moreover, the absence of a welding element on the external face reduces the visibility of the weld zone.

The heating systems of the prior art are placed on the outside of the tube and their activation necessarily results in a pronounced and matt weld zone.

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